Re: wood core coils

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "R Heidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

on 10/12/01 12:00 PM, Tesla list at tesla-at-pupman-dot-com wrote:

> Original poster: "Steve Greenfield by way of Terry Fritz
<twftesla-at-qwest-dot-net>"
> <alienrelics-at-yahoo-dot-com>
> 
> --- R Heidlebaugh <rheidlebaugh-at-zialink-dot-com> wrote:
>> Wood can be made to work for a while, but it will
>> fail. spasks an wood makes
>> carbon. Carbon conducts electricty.
> 
> If you are replying to my post, yes I found that out.
> :') I was also probably overpowering a small coil, it
> was about 12 inches, 10 inches wound length using 32
> gauge wire (only had to start over once due to
> breaking!) with a small round drawer pull for the top,
> driven by a 15KV 30mA neon sign transformer. When I
> had it tuned just right I was getting 2 to 4 inch
> branching sparks into the air, nothing compared to
> what I've seen others do since then but at the time it
> impressed the heck out of me. For about 1 minute, then
> the core failed and it burned a small hole down the
> center of the wood core to ground.
> 
>> Use white PVC
>> plastic pipe to avoid
>> trouble that is common to wood and cardboard.
>> Robert H 
> 
> Something that has been bothering me. I've seen people
> refer to PVC as being able to absorb water, and
> suggest baking it to drive the water out and then
> giving it coats inside and out of sealant
> (polyurethane or laquer, clear only). I also recall
> long ago seeing an article in the ARRL magazine where
> someone had used PVC to make loading coils for a
> multiband dipole antenna, and when he keyed up a KW on
> it the coils failed by arcing a path across the PVC.
> He had a photo of the PVC cores with the wire removed,
> and there was the classic branching pattern burned
> into the PVC.
> 
> So does PVC really able to absorb moisture? Perhaps
> this guys antenna cores failed because he didn't seal
> them. Has anyone tried ABS black pipe, or does the
> black come from carbon for color? Just as a quick test
> for insulation, I was in the hardware store last night
> and rubbed my cotton/poly shirt sleeve on some PVC,
> black ABS and grey (ABS?) plastic electrical conduit
> and then tested it with the hair on the back of my
> hands.
> 
> The concept being that if it was truly nonconductive
> then the static charge I had just caused should stay
> long enough for me to feel it. And if it was even
> slightly conductive it should leak off too fast for me
> to feel it.
> 
> Grey plastic electrical conduit passed with flying
> colors. White PVC I could feel the charge but not as
> much. Black ABS was inconclusive.
> 
> My original intention was actually for a Van de Graf
> generator, but this got me to thinking about Tesla
> coil cores.
> 
> So, can anyone state with authority whether or not PVC
> will absorb any moisture? And whether or not black ABS
> sewer pipe is suitable for Tesla coil cores?
> 
> Thanks,
> Steve Greenfield
> 
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> 
> 
STEVE, FOR WHAT IT IS WORTH I USED 2 in white pvc for 1/4 wavelength balum
coils on the 5 kw transmitter at the tracking at 10 000 ft alt for 3 years
in weather from 90f to -40f snow ,rain, ice, and never had a insulation
failier. wind broke 4 power poles so we put the antenna on the gard rails
and continued to transmit for 6 more mounths. I dont buy your pvc water
breakdown failier theory.
     Robert H.